BS34s

wally · Posted: September 29, 2009, 3:18 am Post subject: BS34s

More carby problems
I have just completed rebuilding the carbs on my 82 special
but of course Im having tuning problems.
Everything has been replaced with new.Had fitted 135 main jets, standard was 132.5 have drilled pilots out to 45
set pilot screw to one & a half turns out.
with this set up with standard air box I had a small amount of blue smoke comming out the muffler on right side first.
went for a ride & after a little while bike seems to stumble down low & run like s*** give it some & i seems to clear & the plugs are very black clean the plugs all all is goog for a little while then the same happens again.
I have now put the 132.5 mains back in but the same still happens I also have adjusted the pilot screw up & down & the same still happensHave checked float level with tube & is correct hight

Q is inlaging the pilot also letting to much fuel in at he small three holes at the butterfly as these hree holes as I see it are not controled by the pilot screw the three holes seem to be before the pilot screw

So I wonder Am I running rich down low becourse of to large a pilot jet & fowling plugs.

Or Do I give up & put both bikes up for sale & buy a new bike?

despecial · Posted: September 29, 2009, 5:05 am Post subject: Re: BS34s

blue smoke tends to indicate oil burning, if it stops after a while your valve guide seals are worn, if it doesnt stop you have oil ring problems

dry black=rich...wet black=oil...but can be a bit of both...you only want the lower 1/3 of the porcelain showing colour

the air mix screw 1.5 turns may need to be opened out to 2.5-feel for the sweet spot

if your pilot jet is too large when blipping the throttle the rpms will drop below your set idle speed before recovering

do a cold set on your bike first-cam chain adjustment, tappet adj, timing, recheck warm then tune in your carbs

despecial · Posted: September 29, 2009, 5:24 am Post subject: Re: BS34s

man, am i slow...wal! YOUR BIKES ARE KAPUT! crate them up and send to me-i need a new boat anchor and you need a reliable ride Wink

despecial · Posted: September 29, 2009, 6:25 pm Post subject: Re: BS34s

2 things to check...is the pilot jet - in the bowl under the black rubber seal loose and is the rubber block sealing properly...the air mix screw at the front of the carb - normally hidden under a plug - has a spring, a washer and an oring below it-screw this right in counting how many turns, then remove it, is the point broken off(if so where is it) and replace the oring after blowing the circuit through...

blackwidow · Posted: December 26, 2009, 11:51 am Post subject: Re: BS34s

despecial wrote:

2 things to check...is the pilot jet - in the bowl under the black rubber seal loose and is the rubber block sealing properly...the air mix screw at the front of the carb - normally hidden under a plug - has a spring, a washer and an oring below it-screw this right in counting how many turns, then remove it, is the point broken off(if so where is it) and replace the oring after blowing the circuit through...

That plug that goes in there why is it plugged can you explain more of what it does??

xsjohn · Posted: December 26, 2009, 12:05 pm Post subject: Re: BS34s

On the BS34 the pilot circuit pulls it's fuel through above the main jet via a hole in the needle jet tower.... if you leave it off then tons of fuel is pulled in above the main jet because of that hole leading to the pilot circuit ....and it's like doubling the main jet.......

xsjohm

gordo · Posted: December 26, 2009, 4:58 pm Post subject: Re: BS34s

John is correct in stating that you are rich on the idle circut.I'm surprised he didn't mention that the pilot circut is working thru the whole rpm range.Stumble off idle is a classic sign of rich pilot. Try turning in the mix screw's, but you will probably have to replace them back to the 42.5. I did the same thing as you did, and ended up breaking a valve spring retainer trying to clear the plug's. If you get yourself a set of John's needles, and follow his direction, your bike will run better than ever. That was my experience.

pamcopete · Posted: December 26, 2009, 5:16 pm Post subject: Re: BS34s

Well, I've never had any trouble with the BS34's on my '81/H. The BS38's on my '78/E are a different story.

I think that the BS34's were built more precisely because they are EPA carbs. I just set everything to factory spec, 3.5 turns each on the idle mixture screws, 135's for the mains, dead cylinder synced and away I go. No stumble, bumble or farting. No flat spots, surging or gurgling.

I use adapted Briggs and Stratton paper filters and EMGO 27" reverse cone mufflers. Plugs are the perfect color (NGK BPR7ES). PAMCO ignition, of course. After syncing, I connect the vacuum barbs together.

So, why not try setting everything to stock, except for 135 mains? I often think that people get lost when they start changing things on carbs. They end up chasing their tails.

I don't pretend to know enough about carbs to tinker with them. You need a complete set of test equipment to really do a good job, other wise you are just guessing.

xsjohn · Posted: December 26, 2009, 5:44 pm Post subject: Re: BS34s

Larger pilots on the BS34 is a good thing........I run a 50 now for a great cruise and decel even with a bit lower CR.........but just a tiny bit of movement in the mix screw goes a long way.......46 is what I usually recommend....lots use a 45 which I found a bit small to suite me.....you said you enlarged the pilot jet...sounds like you bored it too big....what size do you have now.......or do you really know.........

And as for the stock epa needles.....they are staged wrong and have terrible slopes for any serious long rides..... if the pilots and needles and mj are not correct the temps will skyrocket.......the needles come in as you start to accelerate and most of the steady cruise is on the pilot jets..........even on the highway........

xsjohn

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